138

Is there a command or flag to clone the user/group ownership and permissions on a file from another file? To make the perms and ownership exactly those of another file?

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196

On GNU/Linux chown and chmod have a --reference option

chown --reference=otherfile thisfile
chmod --reference=otherfile thisfile
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  • 1
    Could you reference to this answer (and likely cite it) as answer to my question : unix.stackexchange.com/questions/44253/… ? , I think I will be great addition and I'd love to find up-votes there for it. – Grzegorz Wierzowiecki Jul 31 '12 at 20:40
  • @GrzegorzWierzowiecki: probably that question should be closed, but is a little bit different than this and already has answers, so I better do nothing. – enzotib Jul 31 '12 at 20:54
  • As you wish and suggest. Thanks for help, I have never put attention to --reference parameter of chmod and chown before :). – Grzegorz Wierzowiecki Jul 31 '12 at 22:02
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On any unix with GNU utilities, such as (non-embedded) Linux or Cygwin, you can use chmod --reference and chown --reference.

If your system has ACLs, try the ACL commands getfacl and setfacl. These commands differ a little from system to system, but on many you can use getfacl other_file | setfacl -bnM - file_to_change to copy the permissions. This doesn't copy the ownership; you can do that with careful parsing of ls -l other_file, assuming that you don't have user or group names containing whitespace.

LC_ALL=C ls -l other_file | {
  read -r permissions links user group stuff;
  chown -- "$user:$group" file_to_change
}
getfacl other_file | setfacl -bnM - file_to_change
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    You should have ACL installed and filesystem mounted with ACL enabled. – enzotib Sep 14 '11 at 4:03
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    @enzotib At least on Linux, ACL tools will work to copy permissions (but not ownership) even if the source and target filesystem don't support ACLs. – Gilles 'SO- stop being evil' Sep 14 '11 at 6:57
9

Did a bash command based on the response of Matteo :)

Code:

chmod $( stat -f '%p' "$1" ) "${@:2}"

Usage:

cp-permissions <from> <to>...

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  • 6
    Egad!  Where did you learn to say ${*:2}?  Don't ever do that again!  That will fail if any of the filenames contain space (or tabs).  Use "${@:2}".  Also, use "$1" instead of just $1. – G-Man Says 'Reinstate Monica' May 26 '15 at 4:10
  • chmod "$(stat -c '%a' "$fromfile")" tofile in GNU Coreutils, but you might as well use --reference in that case since thestat CLI utility is not POSIX, it even says pubs.opengroup.org/onlinepubs/9699919799/utilities/ls.htmlthat ls -l won't cut it: "The output of ls (with the -l and related options) contains information that logically could be used by utilities such as chmod and touch to restore files to a known state. However, this information is presented in a format that cannot be used directly by those utilities or be easily translated into a format that can be used." – Ciro Santilli新疆棉花TRUMP BAN BAD Sep 2 '18 at 12:10
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If you are not using a system with GNU's chmod/chown (which support the --reference option) you could try to parse the output of ls -l

Here a small script for chmod (if you have a see which supports extended regexes they could be written in a much more readable way ...)

#!/bin/sh

reference=$1
shift
files=$*

# strip the permissions (whith extended regexes could be more readable)
OWNER=$(ls -l ${reference} | sed -e "s/.\(...\).*/\1/"       | sed -e "s/[-]//g" )
GROUP=$(ls -l ${reference} | sed -e "s/....\(...\).*/\1/"    | sed -e "s/[-]//g" )
OTHER=$(ls -l ${reference} | sed -e "s/.......\(...\).*/\1/" | sed -e "s/[-]//g" )

chmod u=${OWNER},g=${GROUP},o=${OTHER} ${files}

UPDATE:

This is even easier using stat:

chmod $( stat -f '%p' ${reference} ) ${files}
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    Instead of parsing ls -l output, you could you could parse statoutput. – jfg956 Sep 21 '11 at 19:51
  • @jfgagne: thanks makes sense I do not know why I didn't think about it in the first place. I updated the answer – Matteo Sep 22 '11 at 5:28
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    You're using *BSD stat syntax here. Your chmod $(stat ...) command won't work because %p alone outputs too much information for *BSD's chmod, use %Lp to output just the u/g/o bits. Something slightly more elaborate would be required for sticky/setuid/setgid bits. – mr.spuratic Jun 7 '13 at 10:17
2

This works for me:

cp -p --attributes-only <from> <to>

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1

I wanted to add an adjustment to Matteo's script. A for loop should be used to validate that the files exist before actually running the chmod command on them. This will let the script error out more gracefully.

I think this is the best option because it can be used for all *nix OSes, like Solaris, Linux, etc.

#!/bin/sh

reference=$1
shift
files=$*

for file in $reference $files; do
  [ -f $file ] || { echo "$file does not exist"; exit 1; }
done

# strip the permissions (whith extended regexes could be more readable)
OWNER=$(ls -l ${reference} | sed -e "s/.\(...\).*/\1/" | sed -e "s/[-]//g" )
GROUP=$(ls -l ${reference} | sed -e "s/....\(...\).*/\1/" | sed -e "s/[-]//g" )
OTHER=$(ls -l ${reference} | sed -e "s/.......\(...\).*/\1/" | sed -e "s/[-]//g" )

chmod u=${OWNER},g=${GROUP},o=${OTHER} ${files}

I found that on one of my Solaris 10 machines, stat was not found. That might be an issue with my configuration though.

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